Seroprevalence of West Nile and dengue virus in the human population of the Bolivian Chaco

To determine the seroprevalence of antibodies against dengue virus (DENV) and West Nile virus (WNV) in the human population of the Bolivian Chaco, we tested 256 inhabitants of two rural communities. The seroprevalence, confirmed by plaque reduction neutralization test, was 7.8% and 2.7% for DENV and WNV, respectively.     

Hemagglutination-inhibiting antibodies in the human population of an endemic area of diphasic tick-borne meningoencephalitis

Summary Sera from 716 inhabitants of the Aland archipelago were examined for hemagglutination-inhibiting antibodies with the diphasic tick-borne encephalitis virus. The antibodies were found in 13.1 per cent of the whole series. There was no significant difference in antibody rate between males and females. It was noted that the antibody rate of the population increased almost linearly with age, which indicates that the human population of the area is exposed to a relatively constant risk of infection. Great local variations in the incidence of the antibodies were found among the residents of neighboring islands. No accumulation by families could be established in the distribution of immunity, which speaks against transmission of the virus through milk in the area.This study was partly aided by grants from the Finnish State Commission for Science, the Samfundet Folkhälsan i Svenska Finland, the Sigrid Jusélius Stiftelse, and the Rockefeller Foundation.     

Extrahepatic manifestations and insulin resistance in an HCV hyperendemic area

Hepatitis C virus (HCV) causes extrahepatic manifestations as well as liver diseases, and contributes to insulin resistance and type 2 diabetes mellitus. The purpose of the present study was to evaluate the relationship of extrahepatic manifestations and insulin resistance in an HCV hyperendemic area. We investigated the incidence of extrahepatic manifestations among 139 inhabitants living in an HCV hyperendemic area in 2002 and compared it to 1999 data for the same inhabitants. Insulin resistance was tested for some non-HCV or HCV-infected inhabitants we had identified during mass screenings in 1999 and 2002. For some of the inhabitants in 2002, we examined records on the prevalence of insulin resistance seven years earlier. The prevalence of extrahepatic manifestations among individuals with positivity for anti-HCV antibodies was higher than among those without HCV in both 1999 and 2002. The prevalence of each extrahepatic manifestation which we identified in 2002 was higher than in 1999. Moreover, in some non-HCV or HCV-infected inhabitants, insulin resistance in 2002 was significantly higher than in 1999. Among inhabitants who had HCV infection with extrahepatic manifestations, fasting insulin levels or HOMA-IR findings seven years prior was significantly higher than for inhabitants who had neither HCV infection nor extrahepatic manifestations (p = 0.03, p = 0.01, respectively). Insulin resistance induces HCV infection, which causes an increase in the incidence of extrahepatic manifestations in HCV-infected individuals.     

Serological studies on sandfly fevers in the Republic of Bangladesh

Blood samples from 160 inhabitants of the Republic of Bangladesh were studied by haemagglutination inhibition (HI), indirect HI, and radial haemolysis in gel tests. The sera were found to contain antibodies to the arborviruses of Sicilian (6.25%) and Naples (1.25%) sandfly fevers and to the Karimabad virus (11.25%) which are transmitted by Phlebotomus papatasi. Antibodies to the Karimabad virus were found among the Bangladesh population for the first time.     

Immunological studies of the functions of paramyxovirus glycoproteins

The HN and F glycoproteins of the paramyxovirus SV5 were purified and monospecific antibodies to each prepared. The effects of bivalent (IgG) and monovalent (Fab) forms of these antibodies on the biological activities of the glycoproteins were determined. Anti-HN antibodies inhibited adsorption of virus to erythrocytes, hemagglutination, and hemolysis. Inhibition of hemolysis was shown to be secondary to the inhibition of adsorption; anti-HN antibodies added after virus adsorption did not affect hemolysis. Anti-HN antibodies inhibited neuraminidase activity, and this inhibition was independent of substrate size in experiments in which virus and antibodies were allowed to react and substrates of different size added, i.e., neuraminlactose and fetuin. This result is in contrast to previous findings with influenza virus in which antibodies inhibited the action of the viral enzyme on the macromolecular substrate only. Thus with SV5, the antibodies appear to inhibit the hydrolytic process directly, rather than sterically hindering the access of the enzyme to large substrates, as in the case in influenza virus. Anti-F antibodies had no effect on virus adsorption or neuraminidase activity, but inhibited hemolysis when added either before or after absorption, confirming the direct involvement of the F protein in the hemolytic process. The inhibition of virus adsorption, neuraminidase, and hemolytic activities by the respective antibodies was accomplished by Fab fragments as well as IgG, indicating that in each case the inhibitory activity was a consequence of a direct effect on individual glycoprotein molecules rather than crosslinking of glycoproteins or aggregation of virions. Both anti-HN and anti-F antibodies neutralized virus infectivity in MDBK and CV-1 cells. Anti-F IgG and Fab, and anti-HN IgG caused essentially complete neutralization in both cell types; however, anti-HN Fab caused only partial neutralization in CV-1 cells.     

Seroepidemiologic studies of hepatitis C virus infection in a population of Okayama Prefecture screened for liver disease

To better understand the spread of hepatitis C virus (HCV) infection, we studied the association of HCV infection with similarly transmissible hepatitis B virus (HBV) infection and with hepatitis A virus (HAV) infection, which is supposed to be related to a nosocomial transmission of HCV. This was done by studying the presence or absence of antibodies to these viruses, as well as hepatitis B surface antigen, in a population of 1,398 inhabitants with abnormal liver function tests or history of liver disease and/or blood transfusion. This group was drawn from a group of 7,905 examinees screened for liver disease in 26 districts of Okayama prefecture, Japan. The prevalence of antibody-positive cases increased with age for those viruses. Small but significantly increased odds ratios were obtained among anti-HCV antibodies (HCVAb), anti-hepatitis B core antibodies (HBcAb) and anti-hepatitis A antibodies (HAVAb). After adjusting odds ratios by logistic regression analysis, a significant association was present only between HCVAb and HBcAb. The distribution of age-adjusted prevalences (AAP) of HCVAb in 26 districts was significantly wider than those of HBcAb or HAVAb. The district-based AAP of HCVAb, but not of HBcAb and HAVAb, correlated significantly with the district-based prevalence of infectious hepatitis having a tendency of chronicity reported in 1953-1955. Adjusted odds ratios calculated by logistic regression analysis of the virus markers showed that HCVAb was significantly associated with a past history of blood transfusion. Thus, the spread of HCV infection is speculated to have been triggered by blood transfusion, particularly from paid donors initially, followed by transmission by nosocomial or close person-to-person contact.     

Distinct functions of antigenic sites of the HN glycoprotein of Sendai virus

Monoclonal antibodies specific for the hemagglutinin-neuraminidase (HN) glycoprotein of Sendai virus were used to examine the antigenic structure of HN and its role in the initiation of infection and immunity. Using 10 anti-HN antibodies, four distinct antigenic sites designated I-IV were topographically mapped on the HN molecule by competitive-binding assays. To relate the biological functions of HN to its antigenic structure, anti-HN antibodies were analyzed for their inhibitory activity in neuraminidase, hemagglutination, and hemolysis inhibition tests. Antibodies to antigenic site I inhibited hemagglutination and one of these antibodies also inhibited neuraminidase activity. Antibodies to site II inhibited neither activity. However, hemolysis an F protein activity was inhibited, suggesting that these antibodies which bind to HN interfere with F-mediated fusion. Antigenic sites III and IV had different effects on the hemagglutinating and neuraminidase functions of HN: Site III antibodies inhibited hemagglutination while antibodies to site IV only inhibited neuraminidase activity. Antibodies to each antigenic site inhibited virus production. Since antibodies to sites I and III inhibited hemagglutination, it is likely that they block virus adsorption. Antibodies to HN site II only inhibited hemolysis, and therefore, may prevent virus penetration. Antibodies reacting with site IV inhibited virus production after virus penetration. Since neuraminidase activity was the only function inhibited, the viral enzyme may be involved in virus release. The fact that site IV antibodies inhibited neuraminidase but not hemagglutination suggests that these sites are distinct.     

Serological and molecular genetic markers of hepatitis C virus in infected donors

The frequency of hepatitis C virus (HCV) markers was determined in donors; the spectrum and activity of specific antibodies (anti-HCV), the distribution of virus genotypes, and HCV RNA concentrations were studied in virus carrier donors. The activity of antibodies in HCV RNA-negative donors was significantly lower than that in HCV RNA-positive donors (p < or = 0.001). There was a statistically significant difference in antibody activities in donors infected with genotype 1b as compared with those infected with genotype 3a (p < 0.001). However, no correlation was found between the concentration of a virus genome and the activity of specific antibodies. The risk for obtaining infected blood donations was determined during plasma screening by enzyme immunoassay (EIA). Our investigations have indicated that the frequency of serological window period donations is one case per 74750 test plasma units and that of HCV RNA-positive donations with low antibody positivity coefficients, which are frequently detectable as seronegative during screening for laboratory errors, is one case per 37375 test units. A combination of EIA and polymerase chain reaction has shown to minimize the risk of contamination of donor plasma with HCV markers.     

The effects of monoclonal antibodies against the hemagglutinin-neuraminidase and fusion protein on the release of Sendai virus from infected cells

Summary Vero cell cultures in Leighton tubes were infected with egg-grown Sendai virus at high multiplicity of infection. Four hours after infection, the cultures were labelled with³⁵S-methionine, after which various concentrations of fourteen and five mouse monoclonal antibodies directed against different antigenic determinants of the hemagglutinin-neuraminidase (HN) and fusion (F) protein, respectively, were added to the medium. Fourty-eight hours after infection radiolabelled virions released into the medium were collected and purified by discontinuous sucrose gradient centrifugations. The amount of virus-bound radioactivity obtained in the various extracellular materials allowed an estimation of the capacity of the different monoclonal antibodies to inhibit the release of Sendai virus. In addition, the release of virions from infected cells was studied ultrastructurally.Based on their serological reactivity the fourteen anti-HN monoclonal antibodies could be divided into four groups. The first group of clones could not inhibit any biological activity of the virus. These clones were binding proximally, near the base of the HN glycoprotein and could not inhibit the release of the virus. The second group blocked hemolysis, but did not block hemagglutination (HA) or neuraminidase (NA) activity. The third group of clones blocked all biological activities of the HN glycoprotein. The fourth group could only block NA activity. With the exception of one of five monoclonal antibodies belonging to the second group, antibodies of the second, third and fourth group were found to bind more distally on the HN glycoprotein. Except for two monoclonal antibodies of the second group they could all effectively inhibit release of the virus from infected cells. Ultrastructurally, these antibodies caused aggregation of virions in contact with the plasma membrane.The five monoclonal antibodies directed against the F protein reacted with four different antigenic sites. These antibodies could not prevent the release of Sendai virus.With 5 Figures     

Different virus-precipitating activities of neutralizing monoclonal antibodies that recognize distinct sites of poliovirus particles

Summary Two neutralizing monoclonal antibodies (4 C 4 and 4 F 2) against type 1 poliovirus, Mahoney strain, recognized distinct antigenic sites of the virus particles; 4 C 4 antibody bound to vertices of native and heated (56° C, 30 minutes) virus of Mahoney strain, while 4 F 2 antibody reacted with specific surface protrusions of native virus of Mahoney and Sabin strains. The difference in the location of neutralization epitopes with which the two antibodies react was confirmed in the neutralization reaction by the use of mutants resistant to 4 C 4 and 4 F 2 antibody.In immune electron microscopy, double immunodiffusion and sucrose density gradient analysis of virus-antibody complexes, the two antibodies showed a marked difference in their virus-precipitating activities. The 4 C 4 antibody recognizing vertices of the virus particle had little virus-precipitating activity. In contrast, the 4 F 2 antibody that bound to specific surface protrusions of native virus aggregated virus particle efficiently.In neutralization assays, however, the 4 C 4 antibody exhibited a slightly stronger neutralizing activity than the 4 F 2 antibody. Thus, it was suggested that the strength in precipitating activities of the two antibodies did not correlate with that in their neutralizing activities.With 6 Figures     

Bile immunoglobulin of the duck (Anas platyrhynchos). II. Antibody response in influenza A virus infections

The capacity of the IgM-like bile immunoglobulin (IgX) of the duck (Anas platyrhynchos) to express antibody activity to H3N2 influenza A viruses, and the dependence of this activity on the co-existence of serum IgM antibodies were investigated. Ducklings infected orally and intranasally at 15-29 days of age with viruses isolated from different host species were examined for haemagglutination-inhibiting (HI) antibodies in biles and sera 16-29 days after infection (p.i.). All biles had antibodies associated with IgX; all sera had antibodies associated only with the 7.8S IgG. Following oral infection of birds 42-days-old with influenza A/duck/HK/7/75 virus, serum HI antibodies were an initial IgM response occurring from 5-12 days p.i., followed by the appearance of 7.8S IgG antibodies. Virus-neutralizing (VN) antibodies in serum were also biphasic; isotype classification was not attempted. Bile IgX developed HI and VN activity. HI antibodies reached peak titres 12 days p.i. and fell to low levels by 24 days p.i. VN antibodies also reached peak titres 12 days p.i., but thereafter persisted at quite high levels throughout the experiment. Development of high titres of antibody in bile coincided with the termination of virus excretion in faeces. These experiments confirm that bile IgX of the duck can function as antibody in response to influenza A viruses, and that its activity appears to be independent of serum IgM. Its possible relevance in determining survival of virus in the intestine is discussed.     

Natural anti-TNP antibodies from rainbow trout interfere with viral infection in vitro

Normal and viral-infected rainbow trout (RT) were tested for serum antibody activity against self and nonself antigens. Particularly high titres of anti-trinitrophenyl (TNP) antibodies were noted, as in other fish species. To analyse this, the anti-TNP antibodies were isolated by affinity chromatography and their capacity to interfere with viral infection in vitro was studied. We selected RT fibroblasts as target cells, and two common pathogenic viruses in trout, a rhabdovirus, viral haemorrhagic septicaemia virus (VHS) and a birnavirus, the infectious pancreatic necrosis virus (IPN). Anti-TNP antibodies were examined for their capacity to neutralize VHS and IPN viruses. Data obtained show that the anti-TNP antibodies, even at high concentrations, only partially neutralized virus. In contrast, when anti-TNP antibodies were assayed for their protective activity using RT fibroblast cells infected with VHS or IPN viruses, results showed high protective activity, regardless of serum origin or of the virus used, when the antibodies were added to the cell culture after viral infection. Therefore, our experiments indicate that the protective activity does not seem to be due to a direct interaction of the antibodies with the viruses. It is suggested that virus-modified cell surface self structures exhibit new epitopes which interact with the anti-TNP antibodies. Such an interaction would allow anti-TNP antibodies to participate in a non-specific defence mechanism against viral infection.     

Lassa virus activity in Guinea: Distribution of human antiviral antibody defined using enzyme-linked immunosorbent assay with recombinant antigen

More than 3,100 households in 27 selected villages distributed in the main geographic regions of Guinea were surveyed for the presence of Lassa virus-specific IgG antibodies (LVA), using an enzyme-linked immunosorbent assay (ELISA) with Lassa virus nucleocapsid protein expressed in insect cells infected with a recombinant baculovirus as antigen. The highest prevalence of LVA (25–55%) was found among inhabitants of tropical secondary forest (areas near Gueckedou, Yomou, and Lola) and guinea savannah (Faranah and Kindia areas), near the southern frontiers with Sierra Leone and Liberia. A much lower prevalence (4–7%) was found among inhabitants of mountainous (Pita, Labe, and Mali) and coastal (Boffa, Boké) areas. We found no discernible differences in LVA prevalence between males and females or among various age groups. Testing of 406 hospital staff members of the eight central hospitals in these areas for LVA revealed a similar distribution of seropositivity among hospitals in various prefectures. The highest prevalence of LVA in hospital staff (29–40%) was in the Gueckedou and Lola hospitals. Sera of LVA-positive persons were tested via Western blot analysis. Antibodies bound predominantly to NP and GP2 proteins. © 1993 Wiley-Liss, Inc.     

Antibodies against dengue virus E protein peptide bind to human plasminogen and inhibit plasmin activity

Both mice and rabbits immunized with dengue virus E protein peptide spanning amino acids 100–119 (D4E) produced antibodies that reacted not only with the D4E peptide itself but also with human plasminogen, as shown by ELISA and Western blot. Sera from dengue virus-hyperimmunized mice and dengue patients also contained antibodies against D4E and plasminogen. Furthermore, such sera all contained plasmin inhibitory activity. Using affinity-purified anti-D4E antibodies and free D4E peptide for competitive inhibition, we demonstrated that the inhibition of plasmin activity was due to anti-D4E antibodies rather than other substances in the sera. Taken together, these results suggest dengue virus E protein amino acids 100–119 are a cross-reactive immunogenic region, and antibodies against this region may interfere with human fibrinolysis.     

Lymphocytic 2',5'-oligoadenylate synthetase activity increases prior to the appearance of neutralizing antibodies and immunoglobulin M and immunoglobulin G antibodies after primary and secondary immunization with yellow fever vaccine.

Primary and secondary immunizations with live, attenuated yellow fever virus vaccine (17D strain) were performed in order to study the course of appearance of virus-neutralizing antibodies and immunoglobulin M (IgM) and IgG antibodies directed against the virus and the interferon-dependent enzyme 2',5'-oligoadenylate synthetase (2',5'AS) activity, determined in homogenates of peripheral B and T lymphocytes. From cellular ATP, this enzyme generates 2',5'-oligoadenylates which mediate degradation of viral mRNA by stimulation of a latent RNase. By day 4 after the first immunization, the earliest and highest 2',5'AS activity was present in the T-lymphocyte fraction. By day 7, the enzyme activity was highest in the B-lymphocyte fraction. Virus-neutralizing antibodies appeared on day 7, and IgM antibodies were present on day 12. After the second immunization, performed 2 years +/- 2 months later, the only significant increase in 2',5'AS activity was observed in the T-lymphocyte fraction. Virus-neutralizing antibodies were present from day 1, whereas no IgM antibodies were detected. By day 12, 80% of the vaccines were IgG positive. In the primary and secondary (memory) immune responses, 2',5'AS activity is expressed in the T-lymphocyte fraction prior to the appearance of antibodies directed against the virus and may serve as an early and sensitive marker of an ongoing virus infection which is otherwise difficult to detect. No change in conventional laboratory analysis parameters, such as in differential blood cell counts or total IgA, IgG, and IgM, disclosed the immune activity in either the primary or the secondary immunization.     

Anti-idiotypic antibodies to monoclonal antibodies that neutralize coxsackievirus B4 do not recognize viral receptors

We have made anti-idiotypic antibodies in rabbits against three mouse monoclonal neutralizing antibodies with specificities for independent epitopes on Coxsackievirus B4. Each of these anti-idiotypic antibodies was found to react specifically with the immunizing monoclonal antibody in radioimmunoassays and did not react with the other monoclonal antibodies. In addition, the anti-idiotypic antibodies specifically inhibited the function (i.e., virus neutralization) of the immunizing antibody. These anti-idiotypic antibodies were tested for their ability to recognize receptors for Coxsackievirus B4 as measured by their ability to inhibit the attachment of radiolabeled virus to cellular receptors. The anti-idiotypic antibodies did not block the binding of Coxsackievirus B4 to monkey kidney cells. Moreover, when tested for their ability to bind to other receptor positive cells, none of the anti-idiotypic antibodies bound above control levels. Anti-idiotypic antibodies did induce a small anti-anti-idiotypic antibody response in mice when tested by radioimmunoassay; however, little if any virus neutralizing activity was found in the sera of these mice. Our results contrast to those reported for anti-idiotypic antibodies in several other virus systems and suggest that not all anti-idiotypic antibodies made against neutralizing antibodies are capable of eliciting an antiviral immune response or binding to viral viral receptors on cells.     

Identification of measles virus-specific hemolysis-inihibiting antibodies separate from hemagglutination-inhibiting antibodies.

The occurrence of antibodies giving hemolysis inhibition (HLI) but not hemagglutination inhibition (HI) was examined in human convalescent and rabbit hyperimmune sera. HI antibodies, which through their interaction with hemagglutinin components display HLI activity, were removed by absorption with Tween 80-ether (TE)-treated measles virus material. This absorption did not change the titer of non-HI HLI antibodies. After removal of HI antibodies from 16 late measles convalescent sera and three batches of gamma globulin. HLI antibody titers showed a two- to eightfold reduction. The titers of neutralizing antibodies were reduced from 1/4 to 1/20 of the original titers. There was a good correlation between the titers of neutralizing and HLI antibodies both in sera from which HI antibodies had been removed by absorption and in sera spontaneously showing markedly higher HLI than HI antibody titers. HLI antibodies with these characteristics could be identified in HI tests when whole virus instead of TE-treated material was used an antigen and anti-antiserum was added to the tests. In contrast to the situation in human sera, antibodies remaining after removal of HI antibodies from rabbit hyperimmune sera against purified virus particles were detectable in neutralization and HLI tests only in the presence of anti-antiserum. However, virus particles from which the major fraction of all envelope projections had been removed by treatment with 0.004% trypsin induced the production of non-HI HLI antibodies active also in the absence of anti-antiserum. TE and formalin treatment destroyed the hemolytic activity of virus preparations and also their capacity to induce a production of non-HI HLI antibodies.